include/xen/xen-front-pgdir-shbuf.h

0001 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
0002
0003 /*
0004  * Xen frontend/backend page directory based shared buffer
0005  * helper module.
0006  *
0007  * Copyright (C) 2018 EPAM Systems Inc.
0008  *
0009  * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
0010  */
0011
0012 #ifndef __XEN_FRONT_PGDIR_SHBUF_H_
0013 #define __XEN_FRONT_PGDIR_SHBUF_H_
0014
0015 #include <linux/kernel.h>
0016
0017 #include <xen/grant_table.h>
0018
0019 struct xen_front_pgdir_shbuf_ops;
0020
0021 struct xen_front_pgdir_shbuf {
0022     /*
0023      * Number of references granted for the backend use:
0024      *
0025      *  - for frontend allocated/imported buffers this holds the number
0026      *    of grant references for the page directory and the pages
0027      *    of the buffer
0028      *
0029      *  - for the buffer provided by the backend this only holds the number
0030      *    of grant references for the page directory itself as grant
0031      *    references for the buffer will be provided by the backend.
0032      */
0033     int num_grefs;
0034     grant_ref_t *grefs;
0035     /* Page directory backing storage. */
0036     u8 *directory;
0037
0038     /*
0039      * Number of pages for the shared buffer itself (excluding the page
0040      * directory).
0041      */
0042     int num_pages;
0043     /*
0044      * Backing storage of the shared buffer: these are the pages being
0045      * shared.
0046      */
0047     struct page **pages;
0048
0049     struct xenbus_device *xb_dev;
0050
0051     /* These are the ops used internally depending on be_alloc mode. */
0052     const struct xen_front_pgdir_shbuf_ops *ops;
0053
0054     /* Xen map handles for the buffer allocated by the backend. */
0055     grant_handle_t *backend_map_handles;
0056 };
0057
0058 struct xen_front_pgdir_shbuf_cfg {
0059     struct xenbus_device *xb_dev;
0060
0061     /* Number of pages of the buffer backing storage. */
0062     int num_pages;
0063     /* Pages of the buffer to be shared. */
0064     struct page **pages;
0065
0066     /*
0067      * This is allocated outside because there are use-cases when
0068      * the buffer structure is allocated as a part of a bigger one.
0069      */
0070     struct xen_front_pgdir_shbuf *pgdir;
0071     /*
0072      * Mode of grant reference sharing: if set then backend will share
0073      * grant references to the buffer with the frontend.
0074      */
0075     int be_alloc;
0076 };
0077
0078 int xen_front_pgdir_shbuf_alloc(struct xen_front_pgdir_shbuf_cfg *cfg);
0079
0080 grant_ref_t
0081 xen_front_pgdir_shbuf_get_dir_start(struct xen_front_pgdir_shbuf *buf);
0082
0083 int xen_front_pgdir_shbuf_map(struct xen_front_pgdir_shbuf *buf);
0084
0085 int xen_front_pgdir_shbuf_unmap(struct xen_front_pgdir_shbuf *buf);
0086
0087 void xen_front_pgdir_shbuf_free(struct xen_front_pgdir_shbuf *buf);
0088
0089 #endif /* __XEN_FRONT_PGDIR_SHBUF_H_ */